1. Field of the Invention
The present invention relates to a composition for forming a roller rubber, a rubber roller made from the composition, and an imaging apparatus including the rubber roller. More specifically, the invention is directed to a composition for forming roller rubber having a decreased amount of a nitrogen-containing compound without a decrease in quality of images produced by an imaging apparatus. The invention is also directed to an imaging apparatus including the rubber roller.
2. Description of the Related Art
FIG. 1 is a schematic view of a conventional electrophotographic imaging apparatus. The conventional electrophotographic imaging apparatus illustrated in FIG. 1 operates as follows. First, a photoconductive drum 11 is charged by a charging apparatus 16, and then an electrostatic latent image is formed on the photoconductive drum 11 by image exposure through a laser scanning unit (LSU) 18. A toner 14 is provided to a development roller 12 by a toner supply roller 13. The toner 14 provided to the development roller 12 is formed in a thin film having a uniform thickness by a toner layer controlling device 15 and is charged. After passing the toner layer controlling device 15, the toner 14 is used to develop the electrostatic latent image formed on the photoconductive drum 11, and the developed image is transferred onto a sheet of paper by a transfer roller 18 and fixed by a fixing device (not shown.) In addition, toner 14 remaining on the photoconductive drum 11 after the transferring process is removed by a cleaning blade 17.
In the conventional electrophotographic imaging apparatus illustrated in FIG. 1, the development roller 12 and the charging apparatus 16 comprise a rubber roller. FIG. 2 illustrates sectional and perspective views of the conventional rubber roller used in the conventional electrophotographic imaging apparatus of FIG. 1.
Referring to FIG. 2, the conventional rubber roller includes a shaft 32 and a rubber layer 31. Conventional rubber rollers can be categorized into ion conductive type rubber rollers and electron conductive type rubber rollers. Ion conductive type rubber rollers are formed of a rubber with low volume resistance, such as hydrin rubber. However, due to the high resistance of the rubber itself, it is difficult to manufacture low resistant rollers using the rubber alone, and thus a conductive additive, such as a conductive polymer material or ion conducting agent, is added to produce a conductive rubber. Electron conductive type rubber rollers can be manufactured by adding carbon black or metal powder, such as copper, to rubber rollers to provide conductivity thereto.
In ion conductive type rubber rollers, the conductive rubber used is expensive and the resistance varies according to surrounding conditions due to obtaining conductivity by ion dissociation. On the other hand, electron conductive type rubber rollers do not use such expensive conductive rubber and have a constant resistance independent of factors such as temperature and humidity in the surrounding environment.
Meanwhile, when rubber rollers formed of NBR, ECO, SBR or EPDM, are produced by sulfur crosslinking, a large amount of volatile organic compounds (VOCs) are formed from side products produced by the decomposition of vulcanizing agents, accelerators, and other additives. Therefore, the formed VOCs may damage an organic photoconductive drum (OPC) contacting a development roller of a electrophotographic imaging apparatus, thereby causing image defects.
Meanwhile, in the crosslinking process of such rubber rollers, a vulcanizing agent, such as sulfur, and a vulcanizing accelerator, such as a thiozole-based compound, a thiuram-based compound, or a sulfonamide-based compound are used. At this time, amine or amide-based nitrogen-containing compounds are formed by the decomposition of the vulcanizing accelerator under vulcanizing conditions including high temperature and high pressure. Nitrogen-containing compounds have an unpleasant odor and cause cracks in OPC coating layers formed of polycarbonate resin. In addition, the amount of total volatile organic compounds (TVOC) is increased which can be harmful.
Accordingly, there is a need to develop a rubber roller which can be produced without formation of VOCs.